Arm & Hammer makes washing soda. It's in the laundry eisle and it's in a yellow box, not the typical orange. It's not available in all markets though. Check out their website for useful information on how to locate the store nearest you that carries it. They give you a UPC number that your store can look it up. Here is the website...

Hmmm. I don't think it would make too much ink. I mean, theoretically of course. Not like I have tried this, lol. But what I meant to say is turning up the saturation in photoshop or your image program of choice should just make the colours darker without affecting the ink volume. Of course, my printer does have an option in it's driver software to set the level of ink it uses on a particular print job. Maybe that is what you're thinking about? I turned that option to the highest setting when I printed some business cards once and they came out literally wet with ink and needed to dry for a while.I don't have the stuff to make the liquid or I would actually test this now! I have been itching to do this since I saw it on a quilting show last year, but I didn't ever get around to buying that stuff.

Hmmm. I don't think it would make too much ink. I mean, theoretically of course. Not like I have tried this, lol. But what I meant to say is turning up the saturation in photoshop or your image program of choice should just make the colours darker without affecting the ink volume. Of course, my printer does have an option in it's driver software to set the level of ink it uses on a particular print job. Maybe that is what you're thinking about? I turned that option to the highest setting when I printed some business cards once and they came out literally wet with ink and needed to dry for a while.I don't have the stuff to make the liquid or I would actually test this now! I have been itching to do this since I saw it on a quilting show last year, but I didn't ever get around to buying that stuff.

Yes, I think you are right. My Canon has a setting to make the print brighter or more vibrant. I might try a few tests on the same photo with Photoshop.